Timestamp not calculating when referencing a calculated (IF) cell

I have read dozens of posts regarding McGimpsey solution to the timestamp problem (http://www.mcgimpsey.com/excel/timestamp.html)

His VBA solution works perfectly if you type a value in the reference cell.

However if the reference cell contains a formula then nothing happens.

eg:

Col B: =if(A1>50,1,0) etc . .
Col C: Uses McGimpsey VBA code to update C1 when A1>50

The Col C timestamp only works if I type "1" into Col B. Nothing happens otherwise.

My actual problem is much more complex than shown above - but I hope this illustrates the point.

Any ideas how to overcome this problem.